SK318792A3 - Method of continual preparing of n-(1,3-dimethyl-butyl)-n- phenyl-p-phenylendiamine - Google Patents

Abstract

The procedure described in this patent is based on the reductive alkylation of 4-aminodiphenylamine with use of 4-methyl-2-pentanone while copper catalyst or acid cocatalyst is present, at the temperature of 18 up to 210 Celsius degrees and the hydrogen pressure of 4 up to 10 MPa, in the cascade created based on the subsequent connection of two up four reaction spaces, where the reaction mixture is being blown by supplied and circulating hydrogen. As a result of cooling closed to circulation hydrogen, the excluded liquid is being divided into the water and organic phase, while the water phase is leaving for the system and the organic phase is recycling into the process. The resulted product is used as an agent able to prevent ozonisation and it is added to rubber strained by mechanical forces.

Description

Technical field

The invention relates to a process for the continuous production of N- (1,3-dimethylbutyl) -N´-phenyl-p-phenylenediamine, which is used as an anti-sonant for mechanically stressed rubber.

BACKGROUND OF THE INVENTION

N- (1,3-Dimethylbutyl) -N´-phenyl-p-phenylenediamine is produced by reductive alkylation of 4-aminodiPenylamine with 4-methyl-2-pentanone according to the reaction scheme:

The overall rate of alkylation is influenced by both reaction stages of the synthesis. The first stage, i. ketimine formation is accelerated by acid catalysts, whether heterogeneous (CS 179 110) or homogeneous (CS 23S B33). The second stage, i. hydrogenation of the imine to the amine is catalyzed by metals, most often copper, platinum or palladium. Both stages are usually carried out in one technological operation.

The preparation of N- (1,3-dimethylbutyl) -N´-phenyl-p-phenylenediamine from 4-aminodiphenylamine is carried out in batch autoclaves at a pressure of 1 to 10 MPa. A solution of 4-aminodi-phenylamine in 4-methyl-2-pentanone and catalysts such as a copper catalyst and an alumosilicate are introduced into the autoclave. The mixture was maintained at a suitable reaction temperature under vigorous stirring under hydrogen pressure until the 4-aminodiphenylamine was completely reacted. The reaction water is predominantly negative since the condensation of the ketone with the amine is a reversible reaction with poorly favorable equilibrium.

Reductive alkylation can also be carried out continuously in a cascade of several tower reactors in which the liquid reaction mixture is bubbled with hydrogen, especially at larger production capacities. The hydrogen and the liquid reaction mixture are fed together from one tower reactor to another. Such a series of three tower reactors system for the alkylation of 4-aminodiphenylamine with ketones in the presence of the above catalysts at a temperature of 120 to 180 ° C and a pressure of 2 to 10 MPa is described in CS 254 739. Under these reaction conditions circulates, evaporates volatile substances, ie ketone, alcohol formed by parallel hydrogenation of the ketone, and reaction water. According to CS 254 739, the hydrogen leaving the last reactor is cooled and the condensed mixture is returned to the first or second reactor, respectively. This continuous process of reductive alkylation of 4-aminodi-phenylamine with ketones is suitable for the 4-aminodiphenylamine-acetone system used in the production of the N-phenyl-N'-isopropyl-p-phenylenediamine antiozonant, while its application in the production of N- (1,3 -dimethylbutyl> -N '-phenyl 1-p-phenylenediamine is associated with considerable complications, although chemically the alkylation of 4-aminodiphenylamine with acetone and 4-methyl-2-pentanone is identical, the preparation of N- (1,3-dimethylbutyl) -N'-Phenyl-p-Phenylenediamine requires a higher reaction temperature of 180-210 ° C because ketimine formation is considerably slower in this case, but the preparation of the two reactors does not differ differently when using a feed reactor, but a significant difference is observed in continuous reductive design. If the procedure of CS 254 739 is followed, the desired reaction temperature can only be achieved with a considerable difference between the temperature of the However, even at the same temperature, reductive alkylation proceeds relatively slower than in a batch autoclave.

SUMMARY OF THE INVENTION

In a detailed experimental study of the conditions for the continuous production of N-phenyl-N'-isopropyl-p-phenylenediamine and N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, it has now surprisingly been found that the shortcomings of the known method of continuous preparation of N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine by reductive alkylation of 4-aminodiphenylamine with 4-methyl-2-pentanone in the presence of a copper catalyst in a cascade of two to four reaction series sparged with circulating and replenished hydrogen it can be removed without costly additional technology interventions by the method of the invention.

SUMMARY OF THE INVENTION The reductive alkylation of 4-aminodiphenylamine with 4-methyl-2-pentanone is carried out at a temperature of 180 to 210 ° C and a pressure of 4 to 10 MPa, and by cooling of the circulating hydrogen the separated liquid is separated into aqueous and organic phases. Phase out of. The system is discharged and the organic phase is recycled to the process. It relies on the finding that a significant difference between the continuous production of N-phenyl-N'-isopropyl-p-phenylenediamine and N- (1,3-dimethylbutyl) -N'-phenyl-p- phenylenediamine in a series of hydrogen-bubbled tower reactors and The resulting drawbacks of the process of CS 254 739 result from the different relative volatility of the components of the reaction mixture under the given reaction conditions. In the case of reductive alkylation of 4-aminodiphenylamine with acetone, acetone and 2-propanol are mainly evaporated into the excess hydrogen stream, whereas in the case of reductive alkylation of 4-aminodiphenylamine with 4-methyl-2-pentanone, the volatile component of the reaction mixture is water. When reductive alkylation of 4-aminodiphenylamine. Using 4-methyl-2-pentanone, the process described in CS 254 739 proceeds, depending on the reaction conditions, 300-1000 kg of water in the form of condensate precipitated by cooling the excess circulating hydrogen per tonne of treated 4-aminodiphenylamine is recycled back to the reactors.

The separation of water from the heterogeneous condensate in the process according to the invention brings about significant positive effects. Due to the high value of the evaporation heat of water, its recycling to the reactors according to CS 254 739 results in intensive cooling of the reaction mixture. This, on the one hand, increases the heat consumption for the tempering of the reactors and, in addition, it requires a higher steam pressure, which may not be possible at all for existing reactors. If the process of the invention is followed, the heat consumption is reduced and the reaction heat of the exothermic reductive alkylation then almost covers the entire heat consumption for evaporating the volatiles into the hydrogen stream. In the process of the invention, only about 10-20X of water is recycled to the reactors compared to the process of CS 254 739.

Another advantage of the process of the invention is to favorably influence the equilibrium and rate of condensation of the ketone with the amine by removing the reaction water. This results in not only an increase in the reaction rate but also a reduction in the formation of the undesired 4-methyl-2-pentanol.

Finally, a significant advantage of the process according to the invention is also a considerable reduction in the negative influence of the reaction water on the hydrogenation catalyst used, which is applied at higher water concentrations, especially above the solubility limit in the reaction mixture. Water can only favor the alkylation process in the case of low selective catalytic systems with a high tendency to hydrogenate ketone to alcohol.

The beneficial effects associated with the separation of water from the condensate eliminated by the cooling of the hydrogen leaving the last reactor are closely related to the reaction conditions, i. to an ISO reaction temperature of up to 210 ° C and a pressure of 4 to 10 MPa. The hydrogen flow through the reactors is defined as in the method of CS 254 739.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the method according to the invention is illustrated by the simplified flow diagram shown in the figure.

The reductive alkylation of 4-aminodiphenylamine with 4-methyl-2-pentanone is carried out continuously in a series of three tower reactors, heated by a steam of 1.2 MPa to a temperature of 180 to 190 °. To the bottom per 1 ton of reactor is

A mixture of 4-aminodiphenylamine with 4-methyl-2-pentanone in a 1: 3 molar ratio, containing 8 kg of a mixture consisting of 80 X copper-chromium catalyst and 20 X alumosilicate cocatalyst, is fed to the first reactor (input A). Circulating hydrogen together with fresh hydrogen is blown through compressor 2 into the lower part of the reactor (inlet g). The liquid reaction mixture, together with hydrogen, flows from the top of the first reactor to the second reactor and subsequently to the third reactor. The residence time in the reactors is 7 hours. 3500 to 4000 Nm ^{3 of} hydrogen are circulated through the reactors

4-aminodiphenylamine. The hydrogen leaving the third cools 4 and returns to the first reactor via the compressor 2. The liquid condensed in hydrogen cooling 4 is separated in the phase separator 5, whereby the aqueous phase is discharged (outlet D) and the organic phase saturated with water is pumped by means of Pump 6 to the second reactor. From the top of the third reactor, the reaction mixture with a degree of reaction of 4-aminodiphenylamine above 99 ° C (outlet C) is discharged. The reaction mixture was filtered from the catalyst and distilled to give the final N- (1,3-dimethylbutyl) -N´-phenyl-p-phenylenediamine.

When operating as described in CS 254 739 with a steam of 1.2 MPa, the reaction temperature reaches only 175 ° C, the reactor power is reduced by 30% and the formation of the unwanted 4-methyl-2-pentanol by-product is increased by 20%.

Claims (1)

PATENT CLAIMS Process for the continuous production of N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine by reductive alkylation of 4-aminodiphenylamine with 4-methyl-2-pentanone in the presence of a copper catalyst and optionally an acidic cocatalyst in a cascade of two to four in series The bubbling and replenished hydrogen spaces are characterized in that the alkylation is carried out at a temperature of 180 to 210 ° C and a pressure of 4 to 10 MPa and the cooling of the circulating hydrogen to separate the separated liquid into aqueous and organic phases, leaving the aqueous phase out of the system; the organic phase is recycled to the process.